The present invention pertains particularly to an operatory stool, such as used in the medical profession, including dentistry, the stool having a curved arm supported on the upper end of an upstanding post adjacent one edge of the stool, the arm being connected to the upper end of the post by means which permits rotation of the arm a limited extent about the axis of the vertical post.
The prior art does not provide many illustrations of a stool having an arm adjustable about an axis of a post extending upward from one edge of the seat. One example of such an arm, however, is the subject matter of prior U.S. Pat. No. 4,025,112, to Hale, dated May 24, 1977, in which a laterally extending member which supports the arm is pivotally connected to a vertical member by means of a slightly conical plug, frictionally disposed within a cup-shaped element, whereby downward movement or pressure upon the plug causes sufficient friction to prevent or control the amount of pivotal movement of the arms.
Related art in the field of stools or chairs includes mechanism in which either a radially or diametrically disposed pin is selectively received in notches to control the position of the seat of a stool with respect to the supporting base and a compression spring normally secures the pin within a selected notch or, in some instances, the circular row of teeth on one member are engageable with a corresponding circular row of teeth on another member of the stool and base. However, when the seat is occupied, the position control members are disengaged and the seat may readily be rotated about a vertical axis with respect to the supporting base. Typical examples of prior patents of this type are found in the following prior U.S. Patents:
U.S. Pat. No. 617,324, Earl, Jr., Jan. 10, 1899 PA1 U.S. Pat. No. 1,666,392, Masury, Apr. 17, 1928 PA1 U.S. Pat. No. 2,764,223, Mischke, Sept. 25, 1956 PA1 U.S. Pat. No. 3,599,924, Schmidgall, Aug. 17, 1971 PA1 U.S. Pat. No. 3,870,271, Bowman, Mar. 11, 1975
It also is old to control the rotation of one member, such as a chair seat, with respect to a base by means of a retractable pin selectively positionable in a circular row of holes or recesses. Examples of such structures are found in prior U.S. Pat. Nos. 1,629,939 to Turner, issued May 24, 1927, and 2,763,523 to Martin et al, issued Sept. 18, 1956.
One additional structure which might be considered pertinent to the present invention is found in U.S. Pat. No. 3,435,783, to Kollenborn, issued Apr. 1, 1976, in which a table top is supported by the upper end of a post and a segmental gear is positionable selectively at various portions of a circular gear for purposes of controlling the angularity of the table top about a horizontal axis.
The present invention includes position control means for the arm of a stool, which includes coengageable members, which, at first glance, appear to be similar to those of certain of the aforementioned prior patents, but the coengagement is in an opposite direction in the invention from those shown in the prior art and explained in detail hereinafter.